LED lighting technology is rapidly developing to replace traditional incandescent and fluorescent lightings. LED tube lamps are mercury-free in comparison with fluorescent tube lamps that need to be filled with inert gas and mercury. Thus, it is not surprising that LED tube lamps are becoming a highly desirable illumination option among different available lighting systems used in homes and workplaces, which used to be dominated by traditional lighting options such as compact fluorescent light bulbs (CFLs) and fluorescent tube lamps. Benefits of LED tube lamps include improved durability and longevity and far less energy consumption; therefore, when taking into account all factors, they would typically be considered as a cost-effective lighting option.
Typical LED tube lamps have a variety of LED elements and driving circuits. The LED elements include LED chip-packaging elements, light diffusion elements, high efficient heat dissipating elements, light reflective boards and light diffusing boards. Heat generated by the LED elements and the driving elements is considerable and mainly dominates the illumination intensity such that the heat dissipation needs to be properly disposed to avoid rapid decrease of the luminance and the lifetime of the LED lamps. Problems including power loss, rapid light decay, and short lifetime due to poor heat dissipation are always the key factors in consideration of improving the performance of the LED illuminating system. It is therefore one of the important issues to solve the heat dissipation problem of the LED products.
Nowadays, most of the LED tube lamps use plastic tubes and metallic elements to dissipate heat from the LEDs. The metallic elements are usually exposed to the outside of the plastic tubes. This design improves heat dissipation but heightens the risk of electric shocks. The metallic elements may be disposed inside the plastic tubes. However, heat remains inside the plastic tubes and deforms the plastic tubes. Deformation of the plastic tubes also occurs even when the elements to dissipate heat from the LEDs are not metallic.
The metallic elements disposed to dissipate heat from the LEDs may be made of aluminum. However, aluminum is too soft to sufficiently support the plastic tubes when the deformation of plastic tubes occurs due to the heat as far as the metallic elements disposed inside the plastic tubes are concerned.
As a result, the current related skills still could not be applied to deal with the above-mentioned worse heat conduction, poor heat dissipation, heat deformation, and electric shock defects. On the other hand, the LED tube lamp may be provided with power via two ends of the lamp and a user is easily to be electric shocked when one end of the lamp is already inserted into a terminal of a power supply while the other end is held by the user to reach the other terminal of the power supply.
A fluorescent tube lamp includes a lamp tube having, traditionally, a circular cross section—for good reasons. The lamp tube is filled with a gas containing low-pressure mercury vapor and argon, xenon, neon or krypton. The pressure inside the lamp is around 0.3% of atmospheric pressure. The inner surface of the lamp is coated with a fluorescent (and often slightly phosphorescent) coating made of varying blends of metallic and rare-earth phosphor salts. The circular cross section provides the lamp tube with structural strength needed to overcome the weight of air on its surface outside the lamp. Other things equal, when a lamp tube provides a bigger inner surface to which fluorescent chemicals are coated, the lamp shines brighter. Lamp tubes having a circular cross section is a sound option. Also, omnidirectional light makes a circular cross section a perfect solution for a lamp tube. An LED tube lamp, however, operates on an entirely different set of principles. Maximizing coating surface is no longer essential for luminous output. Air pressure on the lamp tube becomes irrelevant. Cylindrical lamp tubes, when used in LED tube lamps, induce potential inconvenience if not loss under unfortunate circumstances. An LED tube lamp, whose light is inherently directional, must be correctly oriented before plugging into a light fixture. Cylindrical lamp tubes, unless otherwise pointed out, gives no visual indication of their correct orientation. Moreover, cylindrical lamp tubes roll off the desk easily. Thus, LED luminaries open up whole new possibilities for designing the shape of a lamp tube.
In view of above-mentioned issues, the claimed invention and the preferred embodiments are proposed below.